Telephone system



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N. H. SAUNDERS TELEPHONE SYSTEM Filed Jan. 2. 1931 5`Sheets-Sheet 2 TONE FMT-5.

Dec. 1, 1931. N. H. sAUNDERs TELEPHONE SYSTEM Filed JanA 2. 1951 3 Sheets-Sheet 5 7W OPEP. TEL.

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Patented Ecc. 1, 1931 narra STATES Para NT ,o1-"Fics nonnen I1. sfrunnnas, orlnonnwoen, ILLINOIS, `nssienoa .fro nnsi'invn nonnina acarrear, or cnrcne'o, ILLINOIS, A conronarron or nELAWi-mn TELEPHONE vsr's'rnivr Application inea January 2, 1931. serial no. 506,903.

This invention relates, lin general, to

multi-cnice telephone systems which include.

one or more relatively smallk automatic oflices Vor exchanges, 'and is` concerned par- 157 ticularly with the switching apparatus and inter-oilice trunling facilities provided for such exchanges. The object of the invention is the provision ofnew and improved circuits and apparatus for rendering amore complete and efficient service in such system than 'has heretofore been practica-l.

The 'automatic exchange designed to serve a. small-community and surrounding territory is commonly known as Va community ll automatic exchange or C. and will be designated by the latter term hereinafter. A C. A. X. of this type, upon which the present invention may be considered as an improvement, is disclosed in applicants co-` 201 pending application, Serial No. llh'filed May 8, 1929, now Patent No. 1,805,726, of May 19, 1931. v f I In a C. A.X. 4of-less than one-hundred-line capacity, it is-theusual practice to provide single rank switches which serve asconnectors in local yand incoming calls and as trunk-selectingswitches in outgoing and re-V verting calls* In order to simplify the calling operation it has 'been Vfound desirable tok arrange the C. A. connectors to hunt for an idle trunks-after thereceipt of a single digit. rlhis arrangement has been appliedr to straight Lline connectors, although :in Vthe case of connectors of theparty-line type 'which require an :additional digit for ringing current selection, a two-digit trunk cal-ling code has beennecessary forcalling"ring down trunk lines. The first digit' selects the group of trunk `lines called whereon the 49T connector automaticallylhunts for and connects with an idlejtrunlr. The .second .digit sets .the auxiliary Aringing current selecting switchiof .theconnector .to initiate the signalling. Oneof the f-eatures of .the present invention is the arrangementwhereby the ringing current selecting rswitch associated with c the .connector is automatically set uponthe sei .Je of a ring down .trunk line.

VAnother feature of the invention-.isthe 5G. 'simple andl efficient*arrangement of the C. A. X. connectors so that visual indication .of the class of a calling line is given `r`to the koperator on calls to a manual exchange. Another feature Aof the invention is the arrangement for preventing defective lines from unnecessarily .tying up Vthe switching apparatus of the automatic exchange. Thisfeature vis particularly advantageous ina C. A. X. inasmuch'as the C. A. X. connectors are ynecessarily somewhat more complicated and expensive than the connectors required for large exchanges, which ymakes' it vdesirahleto install the minimum number i of such switchesvas will carry the traflic of Lthe exchange. I. Y

An incidental feature is the association of the apparatus -for controlling the disconnectionY of vdefective lines Y with the primary trunks `instead of with `the switches themselves. This permits the disconnecting arrangement to be readily applied in existing exchanges without lmodification of .fthev switches. It also permits its use in exchanges of any size in connection with Vstandard Vse-flectorsor connectors. f

; The foregoingfeatures and othersinotl specifically mentioned, together, with the operation of the apparatus comprising the invention,will 'be described in detail hereinafter, .reference being had to the accompanyelusive. These drawings show by means .of the usualcircuit diagrams the embodiment of the invention in a system including :a small automatic` exchange and a manual exchange. Fig. l shows a. subsoriberslineand lineswitch, a primary trunk with a control relay 'group` and artimin'g Amechanism lasso- 1ciated Awith the relay group.V Fig. 2 shows a C. LA. X. connector,terminating theprimary trunk yof Fig. L Fig. 3 shows a trunk line connecting to theautomatic and manual exchange, .together jwith the lineswitch associated with the .trunk at the automatic exchange andthe trunk apparatus at the .mannal exchange A dialling cord is also shownin this figure of drawings, K Y

Vfteferringnow to Fig. 1, theV subscribers line shown here may be of the usual multiparty code ringing typewith the bells at the substations bridged from one side of the line to ground. A lineswitch of any suitable type may terminate the trunk. The lineswitch LS, shown, being of the chain ground type disclosed in the J. H. Voss et al., Patent No. 1,809,086, of June, 9, 1931, modiiied in accordance with the requirements of the pres-A ent invention. This lineswitch and other similar lineswitches are controlled by the common master switch MS shown in skeleton form. The various lineswitches have access to trunks of which the one terminating in connector C (Fig. 2) is shown. A group of trunk relays TR is associatedwith this trunk and also with the common timing y mechanism TM.

connector is provided' with a set of four referred to.

-Referring now to Fig. 2, connector C is similar, in general, to the C. A. X. connector shown in Patent No. 1,805,726, previously referred to, modiiied'in accordancevwith the requirements of the present invention. AThe wipers engaging the regular bank contacts and also with a vertical wiper or commutator which during the primary stepping operation engages the contacts of a vertical bank individual to the connector. wiper is so constructed that it engages both the'contact corresponding to thelevel to which the regular wipers are operated and the contact corresponding to the next level below that. Two sets of shaft springs are provided which, for convenience are shown as operating when the shaft and wipers are raised to the ninth and tenth levels, respectively. In practice the shaft springs are made so that they can be adjusted to operate on any desired level. An auxiliary ringing current switch of thety'pe commonly known as a minor switchV is associated with the connector. A This switch selects the various codes of ringing current which are produced by avcode interrupt'er (not shown) of theV type shown in Patent No. 1,805,726, above The subscribers line B and other C. A. X. subscribers lines are accessible in the lirst eight levels of the connector banks. The subscribersline shown may be a -partyline similar in all respects to sublscribers line (Fig. 1). The reverting call switch trunks of which one is shown are accessible in the ninth level ofthe connectork Lineswitch LS1 isof the ordinary rotary type The vertical' whose wipers move only in a forward direction and have no normal or home position. The lineswitch has access to connectors such as connector C in common with a subscribers lineswitch such as lineswitch LS and is used for calls from the manual exchange to subscribers in the automatic exchange. The trunk line terminates in the manual exchange in the trunk apparatus T and is provided with an answering jack J and a dialling jack J1 at the switchboard. Any suitable cord circuit arranged for loop supervision may be used for answering and extending calls over jack J. The dialling cord DC is used only in outgoing calls Jtor controlling the operation o the switches at the automatic exchange.

Having breily described the invention, the operations involved in Aestablishing various connections in a system embodying the invention will now'be described in detail.

rLocal calls The establishment of a connection from substation A (Fig. 1) to substation B (Fig. 2) will be described, by way of example, to illustratethe operation of the apparatus in local calls. In the system shown, the C. A. is of the one-hundred line type and it will, therefore, beV necessary, to dial two ydigits to select a called line. A third digit will be rcquiredto-select the ringing code requiredto signal theV wanted subscriber on the called line. It will be assumed for convenience, that the line extending to substation B terminates in the fifth set of contacts ot the eighth level of the banks in connector C and that the particular station on the line being called, in this instance, is the one .designated by the third ringing code. l

On the initiation of the call at substation A, a ycircuit is completed for line relay 5 of line-switch LS over contacts 19 and 7, lineconductor 1, through the loop at the calling substation, line conductor 2, contacts 12 and 18 to ground. Relay 5 operates and connects lground to the test conductor at contacts '15 conductors 26 to 29. In case the master switch is not in operation or no other lineswitch is in the act of seizing a trunk, ground on the chain circuit by way of contacts 92 will energize magnet 6 of the lineswitch when the Y circuit is completed-as above described. Re-

lay 6 upon operating will force the plunger into the banks thereby closing contacts 21-2l1, and in addition, the magnet discon-y nects relay 5 and ground from the calling line at contacts 18'a`nd 19 and completes a holding circuit for its upper winding at contacts 20.

5" plained hereinafter.

45- jerate in this circuit.

6G sponsive to th Relay 5 is sloW to release and maintains ground on the holding circuit of the magnet until such time as a holding ground can be returned by the connector, as Will be eX- It may be noted at this time that marginal relay 4 does not operate from ground on the test conductor. On the closure of contacts 21 and 24 the calling line loop is extended over conductors 26 and 29,

locontacts 241 and 226, reversing contacts of relay 202, upper and lower windings of relay 203, to battery and ground respectively. Ofi'- normal contacts 240 are included in the circuit of the upper Winding of relay 203 and norlfmally closed contacts 228 of reversing relay 202 are included in the circuit of the lower Winding of that relay. VRelay 203 operates over the calling line loop, connects an additional ground to its lower Winding at conz'oftacts 230 andat contacts 232 connects relay 204 in series with vertical magnet 217. Relay 204 operates and connects ground to the local holding circuit at contacts 234, completes a circuit for the upper Winding ofrelay 203 at zal contacts 235 so that this circuit Will not be open When oif-normal contacts 2 40 open on the rstvertical step of the switch, completes a point Vin the inipulsing circuit at contacts 230, connects ground to test conductor 43 at econtacts 237 and o )ens a aoint in the release circuit at contacts 239. rlhe ground on conduct-or 43 extends by Wayof contacts 35, conductor-23.andcontacts23 to the test conductor of the lin'eswitchto maintain magnet 6 in oper- 35 a ted position after relay 5 releases. Ground on the test conductor byway of contacts 42 energizes relay 32 of the trunk relay group TR, and this relay initiates the operation of the timing mechanism TM by closing contacts 41 4in-as vill he explained hereinafter. Referring again to the connector it Will be recalled that rei-tical magnet 217 has been connected in series with release relay 204. Due to the high resistance of relay 204 the magnet does not op- Relay 207 is connected to the impulsing circuit at contacts 247 in parallel with magnet 217 and is also in series With relay 204 but does not operate due to the high resistance of ther latter relay. Relay 5G 213 operates, from ground by Way of contacts and off-normal contacts 295. This relay in operatitng completes the impulsing (ircuit for the vertical magnet at contacts 291 and, at contacts 293 connects dial tone to 551 loafer talking conductor of the trunk.l The dial tone is audible to the callingsubscriber and indicates that the apparatus is ready'to receive the dial impulses.- Y

'l1 he foregoing operations takeV place reinitiation of the call. The calling subscriber will new dial the lirst digit of the called number, in this case the digit 8, and the circuit of relay 203 of theconnector Will be interrupted accordingly H .'Each time' 6@ relay 203 restores in response to an open 291 to vertical magnet 217. The magnet Willy operate in the usual manner and raisethe Wipers of the connector step-by-step to the called level. Relay 20.4 Will be short-circuited at each impulse by ground through contacts .31. This shortA circuit renders the relay sloW-to-release .and consequently the relay remains operated throughout the series offimpulses. Relay 207, which as previously stated, is connected to the impulsing circuit in parallel With the vertical magnet operates in response to the iirst impulse and remains operated throughout trie series of impulsesA as its connection to relay 204 renders it slowto-release. Relay 207 completes a holding circuit by Way of contact 249 and 290 to maintain relay 213 operated when off-normal contacts 295 open on the first' vertical step of the Wipers. An additional ground is connected to the lower Winding of relay 203 at contacts 251,- a circuit is completed for relay 210 at contacts a point of the circuit of relay 203 is opened at contacts 254, and ground is disconnected from the off-normal contacts of the auxiliary switch at contacts 255. Relay 210 operates and completes a number of circuits, thek only one of which is of any utility at this time is the auxiliary impuising circuit by Way of contacts 250 and 274. This auxiliary circuit is to prevent any interference With the impulsing which might be caused by momentary operation of relays 200 or 209. Upon the first vertical step of the wipers oil-normal contacts 240 and 295 open and contacts 233 close. rEhe opening of contacts 240 is Without any particular results at this time since the circuit for relay 203 now includes contacts 235. Release inagnet 218 is connected to trunk conductor 44 on the closure of contacts 233. This conductor extends to relay 34 of the trunk relay group and the relay operates in series With the release magnet. Ene to the high resistance of the relay the release magnet does not operate at vthis time. Relay disconnects relay from conductor 43 at contacts 42 and relay 33 releases and restores the timing mechanism Ato normal condition.

At the end of the iirstseries of impulses relay 203'W1ll remain operated and 'again con-r nect relay 204 in series with relay 207 .and vertical magnet 2i7. Relay 207 does not yremain energized in series with relay 204 and consequently restores after a short interval and opens the circuit of relays 213 and 210.

Rela 213 restores disconnects dial tone frein Vand opens the previously traced auxiliar-)1 impulsing' circuit at, contacts 274. y

The'calling subscriber new dials the second VAcut-ofi? relay of with the called line, closes apoint in the cir-- digit of thecalled number, that is the digit 5,

and relay 203responds as in the previous case. The impulses are repeated over the impulsing circuit previously traced Which now` 209 pren :es a locking circuit for itselin at contacts il, prepares a short circuit for the lovver Winding of relav 2l0 at cont-acts 266 to mal the. ry slow-to-releasc, opens the iinpulsnigA circuit at contacts 267, opens a point in the release circuit at contacts 269 and connects busy tene to the lower talking conductor or the trunk by Way oi"x contactsY lV hen relays 207 and 210 270, 28e, and restore shortly alter the last impulse of the series relay 209 wi i loclr up over contacts 273 a tone the line will yoc audible to the calling subscrioer who is expected to hang up and rcleasethe connection.

TWhen. the called subscriber hangs up, the circuitor relay 203 will be opened and that relay .willrestore Relay 203 opens the circuit ot relay 204i which also restores and disconnects ground from the local holding circuit at contacts Relay 209 releases and a circuit is completed for release magnet 218 by Way of contacts 224i, 229, 239, 269, and `ldagnet 218 Will restore the switch Wipers normal position in the usual manner and its circuit will be opened at olf-normal contacts 233 which open When the Wipers reach normal positions.

ln the event that thecalled line is not busyv when connection is extended thereto as above described, test Wiper 110 Will find battery through the cut-off relay of the hneswitch on the test contact instead of ground as in the previous case. Relay 209 consen oueutlv vril not operate and when rela s 207 A.\,o).v u L c- L y -Y series, a circuit will be completed from on the test contact, Wiper 110, con- 'r and 271, lower Winding of relay to ground on the Relay 211 operates in theabove circuit, connects direct ground to the test-'wiper at contacts 278 to operate the the lineswitch associated cuit of pick-up relay 215 at contacts 279, `disconnects rotary magnet 216 from the impulsing circuit at contacts 282 andV extends this circuit by .Way of contacts 281 to stepping `0 restore shortly after the last impulse magnet 219 of the auxiliary switch, opens a point in the dial tone circuit at contacts 283, and opens a point in the busy tone circuit at contacts 284.

rlhe calling subscriber will now dial the last digit of the called-number, in this case the digit 3, and relay 203 Will respond and transmit impulses over the previously traced impulse circuit to stepping magnet 219 of the auxiliary switch. Magnet 219 Will respond to the impulses and step Wipers 223 and 238 orn the auxiliary switch around to the third set of contacts of the bank. Relays 207 and 210 Will again operate during the series of im pulses, the former relay opening a point in the circuit ot relay 209 at contacts 255. Off-normal contacts 200 close when the Wipers ofthe auxiliary switch are moved from normal po sition, and, when relay 207 restores shortly after the last impulse of the series, an obvious circuit is closed for relay 209 and the relay operates. Relay 209 completes a locking circuit ior itself atcontacts 264, closes a point oi" the circuit of .relay 215 at contacts 265 and opens the impulsing circuit. at contacts 267. rl'he busy tone circuit is closed at contacts 270 as explained in the previous connection but this is Without eliect sincerelay 211 is encrgized and contacts 284: are open.

interruptor NT is associated with the ringing Acurrent interrupter and is arranged to send out a groundimpulse preceding each series of ringing current impulses constituting a code. The code interrupter which may be of any suitable type has not been shown but is indicated bythe broken section of the conductor extending to generatorGEN. At the proper time, therefore, a. ground impulse 'from interrupter lNTby Way of contacts 265,279, 104, and 289 Will operate relay 215. This relay will lock to the local holding circuit at contacts 105 and will complete the ringing circuit for signalling the called sub# scriber. The ringing circuit in this case may be traced from the grounded generator, third contact of the bank engaged by Wiper 238 of the auxiliary switch, contacts 299 and 107, Wiper l13, line conductor' 117, through the bells and condenser at the substation, to ground. The lower Winding of relay 213 is connectedby Way of contacts 297 and 102, Wiper 109, to line conductor 119. Ringing current is now applied to the called line over the above circuit in accordance With the code selected by the digit 3. Ringfback-tone is transmitted to the calling subscriber over contacts 103 to indicate that .the called subscriber is being signalled.

TWhen the called subscriber answers a di- 'rect current bridge is closed across the line at the substation and relayv213 operates over the called loop from ground superimposed on the ringing current. Relay 215, in` operating, opens the circuit of relay 213, and locks over itsupper Winding in series Withrelay.

: called loop.

212 by way of contacts 290 `and 280. Relay 2112 operates and closes points in the talking circuit at contacts 286 and 288. Relay 215 rel-eases following the operation of relay 213, opens the previously traced ringing circuit and completes the talking circuit at :contacts 101 and 108. Relay 205 feeds talking -battery to the called subscriberand operates over the A circuit is closed at contacts 2113 for relay `202 which operates and reverses the conne-ction of relay to the trunk. Relay 202 alsoapplies an additional ground to the local holding circuit and opens a point in the release circuit. n y

The calling and called subscribers may now conve-rse. lny case the Called subscriber l-i-angs up lirst, relays 205 and 202 willre'lease but the switch will not be restored to normal since the release circuit will be maintained open at contacts 239. In case the calling subscriber hangs up first relays 203 and 204 will resto-re, but relay' 202 will maintain an open point in the release circuit at contacts 229. hen both subscribers hang up the relays above-referred-to will release and a circuit will be closed by way of contacts 224, 229,239, and v268 for release magnet220 ofthe auxiliary switch. Magnet 220 will operate to restore the wipers of the auxiliary switch to normal in the usual manner. Off-normal contacts 200 yopen when the switch wipers reachnormal position and relay 209 restores, its locking circuit having been opened previously by Y, the releasefof relay 204. Relay 209 on restoring transfers the release circuit over lto release magnet 218 at contacts 269 and magnet v218 restores the wipers of the connector.

to normal position in the usual manner;

In the foregoingexample it was assumed that the called subscriber was the one designated by the inal digit 3. In calls to other subscribers on this line, for example to the subscriber designated bythe final digit 8, the operations involved inV setting 4up they connection will be exactly the same as previously described, except that the wipers of the :auX- ili'ary switch willbe stepped to the eighth contact of the bank. In' positions 6 to 10 wiper 23 encounters grounded contacts and a circuit is completed for relay 211`which operates and reversesl the connection of the ringing current generator and-relay 213 with respect to the wipers. The ringing current 1s,

S- therefore, applied tothe upper wiperby way of contacts 296 and rings the bells atthe sub,- stations bridged to line conductor v119. v The operation of relay 213 von theKanswering of the call and the talking circuit are exactly 6@ the same as described for the previous connection.

.made in the same manner as in the system de-f scribed in Patent No. 1,805,726, previously` to that shown in the above referred to patent.

The operations resulting on the initiation of a call 'are exactly the same as described for local connections. It will be assumed that the subscriber at substation A is the calling subscriber Vand that lineswitch LS has seized 'connector C. The called subscriber dials the digit 9 and the wipers of the con` nector are stepped to the ninth level exactly as in the previously described connection. ln' calls to this level, however, vertical wiper 111 bridges vertical bank contacts 115 and 116 and the shaft springs designated LEV.9 are operated. Relays 207 and 210 are energized during the impulsing, as in previous instances, and when wiper 111 bridges contacts 115 and 116, ground over this wiper by way of contacts 277 and 272 operates relay 209. Relay `209 completes a short circuit around the lower winding of relay 210 to make this relay slow-to-release. A short time after the last impulse of the series, relay 207 restores and completes a circuit from ground oncont-acts 116, wiperv111, contacts 285, 275, and 254 for relay 208. Relay 208 energizes and completesr a holding circuit for relay 210 which incidentally has not yet had time to restore. Relay 208 also completes a locking circuit for itself by closing contacts 262- and at contacts 260 completes a circuit for rotary magnet 216. Magnet 216 operates and steps the wipers of the switch in 0n the first set of contacts of the called level. Magnet 216 onV operating opens the circuit of relay 208 at contacts 285, land relay 208 consequently rest-ores and opens the circuit of the magnet at contacts 260. Wiper 111 is disengaged from the vertical bank contact upon the first rotary step ofthe wipers and the circuit of relay209 is opened at this point.

he further operation will now depend on whether the first trunk of the called level is busy or idle. Assuming that the trunk is busy, wiper 110 will iind ground' on the test Contact and relay v209 will remain energized. lt will be noted that the test contacts engaged by wipers 110 and 112 are connected to the same test 'conductors and consequently when the trunk is busy, wiper 112 will also find ground` andwheu magnet 216 restores this groundwill reoperate relay 208. Relay 208 willagain complete a circuit for relay 210 and magnet 216, and the 'wipers' will be advanced 'another step. This stepping operation will be repeated until an idle trunk is found or until the last trunk of the group is reached. rl`he last trunk of the group is marked by leaving the ktest cont-acts engaged by wiper 112unconnected. jY Consequently, when this trunk is reached relay l209 will reina-in operated but no circuit will be completed for relay 208 and no further stepping will take place. Relay210 will release a short V.time after the `last rotary-step and relay 209 will remain locked to ground on the local holding circuit. Y Busy tone will be applied to the lower talking conductor of the trunk by way of contacts 270, 284, and 294 to inform the calling subscriber that no trunk is available at this time. The calling subscriber' will then hangup and release the connection in the saine manner as described for calls to abusy line.

-vrAssuining that an idle trunk line in this level is accessible, for example the trunk line comprising conductors 120-122, when the wipers of the switch engage the set ot contacts' 'terminating this trunk, test wip-er 110 will lind no ground and relay 209 will restore. Vhen relay 210 restores shortly after the release ot relay'207, a circuit will be completed from battery on the testconductor of the seized trunk, wiper 110, contacts 277 and 271, upper winding of relay 201, contacts 256 and 263 to ground on the local holding circuit. Relay v201 on operating,- completes a holding'l circuit for its lower winding including the test wiper 110 and also extends the holding circuit over conductor 43 to the magnet 6 of the lineswitch. Talking conductors26 and29 are disconnected from the relay 203l and extended by way of contacts 242 and 225. directly to wipers 109 and 113.

Relays 203 and 204 release but the release of the; switch is prevented at this time since the release magnet circuit is open at contacts 224. The remaining impulses required to set the i'everti call switch are transmitted over the talking conductors of the switch in the usual manner. The release of the connector and lineswitch is prevented by the ground fed back 'over the testrconductor from the revert'- 1 ing call switch which Vmaintains relay 201 operated. rThis same ground extending over conductors 43, contacts and conductor 28, maintains magnet 6 to the lineswitch operated. -The operation of the reverting call switch is well known and will not be described Ground will be removed from the to t f r i L swi ci *est conductor when the leve t ng call t l is released after theconnection has been completed and relay 201 will-release.' The circuit of release magnet 218 will be completed at the plunger of the switch .will be withdrawn tromthe bank by its restoring spring inthe well known manner.

Trunk Calls Inthe foregoing connection no reference was made to the discriminating service feature of the system'. This feature is adapted to 'function only in trunk calls and will be described in connection with a call from subscriber A to the operators position (Fig. 3). One class of lines is marked by ground on the discriminating contact of the lineswitch andthe other marked bythe absence of ground on thesecontacts. A restricted line will have this contact connected to ground tacts 114 and 115 and shaftsprings designated A Y LEV.'0 will be operated. Relays 207 and 210 will operate during the stepping of the switch and at the completion of the stepping operation, circuits, as previously described,

willbe completed over wiper 111 for relays 209-and 208. The switch wipers will be given an initial rotary step in the same manner as described for reverting calls and the hunting operation will also be performed as described in connection-with such calls. When an idle trunk is found, for example the trunk comprisingconductors 301-303, wiper 110 will find battery potential on the test contact and relay 209 will restore. When relay 210 restores shortly after the release of relay 207, the test wiper will be extended by way of contacts 271 to the vlower winding of relay 211 and this relay will operate in series with the cutoff relay of the lineswitch associated with the trunk. Relay 211 on operating, completes a circuitfor relay 206 by way of contacts 27 6 and shaft contacts 248, connects direct ground to the test wiper at contacts 278.

tooperate the cut-0Hl relay of the lineswitch associated with the trunk, closes a point in the circuit koi" relay 215 at contacts 27 9, completes a locking circuit foritself and prepares a holding circuit for relay 213 and relay 212 at contacts 280, disconnects rotary magtacts 282 and extends this circuit by way of contacts 281 to stepping magnet 219 of the Y tends this circuit to which stepping magnet 219 has been connected to ground at contacts Magnet 219 operates and advances the vwipers of the auxiliary switch one step. A circuit is closed for relay 209 on the operajumper 25, contacts 22, and conductor tion oi oil-normal contacts 200 and this relay operates to open the circuitof the stepping magnet at contacts 267. Relay 209 locks up by way of contacts 264 and at contacts 265 connects the pick-up interrupter through to relay 215. rupter lNToperates relay 215, and the relay locks by way of contacts 105 to the grounded local holding circuit. Ringing current `is nourtransmitted over the first bankcontact engaged by wiper 233, contacts 299 and 107, wiper 113, trunk conductor 303, contacts 349, condenser 312, winding of relay-303 to battory. Relay 30S operates and locks mechanically, completing a circuit at contacts 321 for line lamp L2. Lamp L2 glows to notify-the operator of an incoming call. Y A

Upon noting' the lighted condition of lthe lamp ing the plug of an ordinary answering cord into jack tl, thereby completing a circuit for the upper winding otrelay 309. Relay 309 operates and locks over its lower windingand contacts 326 to ground on the sleeve of the 'f jack and plug'. Relay 309 closesa circuit by wa i oli' contacts 322 and 317 for relay 30T and that relay operates and by means oi' the interlocking;i mechanism 320 restores the armature of relay 303 to normal. Lamp L2 is extinguished at this time. In addition to completing the foregoin-rr circuit,relay 309 at contacts 327 connects polarized relay 310 across the talking conductorsA of the trunk.

The ring-cut-oti' relay in the connector now the operatingI conditions of the particular system involve-d.

1n the case ot a call from a restricted line to the operator, the connection will be set ug ink exactly the same manner vas described above tor a call from a non-restricteil line ln this case, however, ground by way ot be extended by way of contacts 244 'to 214, when relay 206 operates on the sei the trunk. Relay 214 on operating'wi verse the connection ot the ringing current generator and rino-cut-otl' relay with respect to the wipers. When relay 215 operates in responseto the pick-up impulse, as previously described, ringing` currentwill b'e transmitted over wiper 233 of the auxiliar-y switch in first position, contacts 296 and 102,

A ground'impulse from inter-- the operator answers the call by insert-` Lthis yconnection is the same as wiper 109, trunk conductor 301, contacts 347, condenser 311, winding of relay 304 to ground to operate that relay. Relay 304 is arranged tov lock its armature mechanically when operatedV and is unlocked by the interlocking mechanism` 315, controlled by relay 305. Relay 304 on operating, completes a circuit at contacts 314 for the lamp L2 and the lamp glows to indicate the incoming call.

The operator on noting the lighten condition of the line lamp will answer the call as previously described 'whereupon relay 309 will operate and lock to the sleeve of the ack and-plug. V A. circuitl will be closed over contacts and 313 for. relay 306. Relay 306 operates, closes a circuit for lamp L1 at contacts 316. opens the circuit of relay 307 at contacts 317, closes a. holding` circuit for itself at contacts 318 and completes circuit for relay 305 at contacts 319. Relay 305 operates au d unlocks the armatures of relay 304, thereby extinguishing' lamp L2. The glowing; of lamp L1 indicates to thejoperator that the line .is in the restrictedclassand the connection may be then handled in the manner required by local conditions. The release olf previously described.

Ia/mm1 to automatic calls To extend a connection from the manual exchange to,` a subscriber at the automatic exchancgeythe operator will insert the pluar of a i `,cular cord circuit into the jack ot :in idle trunk lineftor example the jack .l of truuk line T. Relay 309 will. operate over the battery 'iced loop ot the cord' and lockt-o ground on the sleeve ot the jack and cord by way of ycontacts 326. `Polarized relay 310 is thereby bridgedV across the trunk conductors and line relay 331 ot' lineswitch LS1 at the automatic excl ange will operate over a circuit includ.- contacts 337. trunk conductor 301. contacts 347'.V upper lett-hand wndino-V of repeating' coil windings of polarized Vrelay 310.l contacts 327. lower lett hand winding` ot the repeating` coil. contacts trunk conductor 303. and contacts 342 to ground. Relay 331 in operating completes a circuit at contacts tor and magnet 336 in series, and at contacts 334 connects test wiper 344 in the circuit at a point between the magnet and relay y ln case wiper .andino ou the cont-acts of a busy trunk at this time1 j ound on the test contact will operate mag'- net w" and shunt relay llalanuet 336 in oper. in j opens its own circuit at cont-acts 335. and on restoring, steps the wipers of the .-...ch ahead one step. This hunting operation will be repeated until an idle trunk is louud. whereupon wiper 344 will no longer find ground 'on thecontact and relay 332 will operate. The resistance of relay 332 is such that magnet 336 will not operate in series therewith. Relay 332 connect-s the talking conductors ot the line through to Wipers 343 and 345 at contacts 338 `and 341, opens the circuit oit' relay 331 at contacts 337 and 342, and'disconnects test Wiper 344 from its loWer T terminal at contacts 339 and connects it to its 10." trunk line.

upper terminal at contacts 346. .Relay 331 Will release after a slight delay which is sutlicient to maintain relay 332 operated until a holding ground is returned over the seized Linesvvitch LS1 has access to connectors, such as connector C (Fig. 2) and this switch operates on seizure by lineswitch LS1 in exactly the same manner as When seized by l@ a local subscriber in the automatic exchange.

The operator now inserts the plug P of the dialling cord DC into the jack J1 of the trunk line in use. Ground on the ring contact of t. pluo' energizes relay 346 and this tt: l.

? relay transiers the talking conductors of the 2.52 ot the aclr and plug, retardation coil 353, and

trunk to the tip and sleeve contacts of the jack at contacts 343 and 356, respectively. The connector switch is now held operated over a circuit including the tip and sleeve contacts impulse contacts 351 of the calling device CD. The operator now dials the number of the Wanted subscriber in the usual Way and connector C operates to extend the connection in 393 exactly the same manner as described for local calls. Retardation coil 353 is shunted by off-normal contacts 352 during the impulsing to improve the quality of the impulsing. After setting up the connection as above V3,5! described, the operator Will Withdraw plug P from the dialling jack and relay 346 Will restore. The talking conductors of the trunk are nov7 extended by Way of contacts 347 and 349 and the left-hand windings of re- 40T peating coil R to relay 310.V Relay 310 does the called subscriber hangs up battery is again reversed over the trunk line and relay 310 restores, again closing the bridge across the talking conductors or the cord to give the disconnect supervision. The operator then withdraws the plug from jack J and relay 309 releases. Relay 309 yopens the bridge across the trunk conductors thereby permitting the release of the linesyvitch 0 and a connector.

Defective Zine lockout In case a line becomes short circuited or the receiver is accidentally knocked from the switch-hook and also in case the negative 5 Vside of the line becomes grounded, the lineswitch Will operate in the same manner as when a call is initiated and extend the line to an idle connector. A short circuit on the line terminating in substation A for instance, Will cause lineswitch LS to operate and seize an idle connector Which may be the connector C. The operation of the lineswitch LS, trunk relay group TR, and connector C are exactly the same as described for a call initiated by the subscriber at substation A. Referring to thev previous descripton it will be recalled that relay 33 operated from ground on the holding conductor and that relay 34 operated on the first vertical step of the switch and disconnected relay 33. In the present instance since the connection has been extended as the result of trouble on the line, no impulses will be transmitted to the connector, hence, relay 34 Will not be op erated. Relay 33 on operating closes a point of the circuit of relay 32 at contacts 40 and at contacts 4l completes a circuit by Way of contacts 83 for relay 59. Relay 59 operates and completes a circuit via contacts 80, 74, and 82 for relay 58. Relay 58 is provided with a Weightedv armature spring which vi brates when the relay operates, thereby intermittently closing a circuit :for relay 56 at contacts 78. After a period of vibration which depends upon the vadjustment oit the Weight on the armature spring, contacts 78 Will remain closed llong enough to permit 'relay 56 to operate. Relay 56 on operating,

completes a circuit for relay 57 at contacts 72. Relay 57 operates, opens the circuit of relay 58 and completes a circuit by Way of contacts 76, 75, 69 and 64 for relay 54. Relay 58 releases as soon as the circuit is opened but relay 56 is sloW-to-release as Well as sloW-to-operate and maintains the circuit of relay 57 for a short time after its own circuit is opened. Relay 54 operates, prepares a locking circuit for itself and relay 53 in series at contacts 67 and opens a point in the initial energizing circuit of relay 32 at contact 66. This is to prevent interference with calls on other trunk lines to which the timing mechanism TM is common. yRelay 53 cannot operate at this time since it is short-circuited by the ground from the'contacts of relay 67. Relay 56 eventually restores and opens the circuit of relay 57 and the latter relay also releases after a slight delay. Ground is thereby removed from the upper terminal of relay 53 and that relay operates in series with relay 54 to ground at contacts 85. Relay 53 transfers the circuit over which relay 54 Was initially operated to relay 52 by Way of contacts 65 andv 61. Meanwhile, relay 57 has released and again closed the circuit of relay 58 which again operates to initiate the operation of relays 56 and 57. Relay 57 on operating transmits ay second ground impulse over the previously traced circuit to relay 52. Relays 56,. 57, and 58 again restore as in the pre- Vious instance :and relay 52 operates in se-` time after its. circuit is opened. A circuitis completed by way of contacts 68 and. 39 for relayv 31 and a circuit is completed for relay 60at contacts 71. Relay' 60 is slow-to operate and after a slight delay `operates to open thecircuits of relays 51--54 at contacts 85, opens. thel circuits of relays 58 and 59. at contacts 82 and 83, respectively, and

2.a opensa point in the energizing circuit of relay 32"at contacts 81. Relay 3l on operating connects'high potential positive battery commonly called booster battery to holding conductor 28.` Relay 4 of the lineswitch cuit for its upper winding by way ot contacts 8, line conductor l, through the short circuit onthe line,- conductor 2, contactsl3, to ground. The talking conductors are disconnected from vthe conductors of the lineswitch at contacts??` and l2. Test conductor 3 is disconnected from the holding circuit at contacts 94 and a direct ground is applied to the conductor at contacts l0, and a circuit is closed for lamp L at contacts l1. VThe opening of the line conductors permitsthe line and release relays ofthe seized `connector to restore to anormal and remove ground from the .holding conductor. When this. oc 40 curs relays 32 and 33 rest-ore. Relay 31 is: operated only momentarily and the booster battery is disconnected from the holding conductor iontherelease of therelay. Magnet Gioi? thelineswitch restores and the plunger is withdrawn. from the. banks by itsrestoringl spring. The trunk extending to the connector is now available. for other calls, while cutfoii-relay 4 remains locked up over the linewand prevents theline L.from again seizing a connector. rlhe line is marked busy to connectors by the ground on test conductor 3. Lamp. L glows. to indicatey tothe eX-' change attendant that the. line.: associated therewith is locked.outwbecausc oiv trouble. Then the'troubl-elis cleared .from the line the line is automatically restored to` service upon the'release of relay 4. Therelease of relay 33,v as previously mentioned, permits the timing mechanism TM to restore.

What is claimed is: l. In a telephone system,a two conductor trunk line, two classes ofcalling'lines, kany automatic switch` for extending connections from a calling line to the'trunk line', means inthe switch responsive'to-'a callY fromva line now operatesaand completes a holding cir-` ot one class for applying signalling current. to one conductor oi' the trunk line, and means' in the'switchA responsive to a call from :a line of the other classfor :applying signalling pui-rent to the other conductorof theitrunk me. A f

V2. In `a telephone system, an.` automatic switch accessible to calling lines of twoV classes `fory extending connections vIto-l a trunk line, means 1n the switchV for automatically applyinw ringing Vcurrent tothe \trunkline,n

and means in the switch for determiningrthe side oi' the trunk line to which ringing cursi:V

rent is to be-vapplied, said last meansbeing controlled by theclass of thecalling line.

3. In Ya telephone system, an automatic switch for extending vconnections to a trunk line, means. in the switch for normally.v applying ringing current' to one side'of the trunk line, and means in the switchcontrolled bya preceding switchfor causing said first means:

to apply yringing current to theother side of the .trunk line.- l 4. In 'a telephone system, atwo-condnctorA trunk line connecting an automatic ex-V change anda manual switchboard, an auto-vv matic switch at' the exchange for :extending callsof two classes over the trunk line and for applying signalling current to one orf the other-ot the. trunl conductorsvdepending on the, class of the call, a signal atfthe switchboard operated'responsive: to the applicationv of' signalling current to either trunk conductor when a call is extended `over the trunk line, and. 'a second signal at the switchboard-f connected to a lparticular one of the trunk Y conductors.

5. vIn a telephone system, a two-conductor trunk line co-nnecting'an*4 automatic exchange.

and a manual' switchboard, :an automatic switch atthe. exchange for yextending kcalls oftwo classes over the trunkline and for applying ringing currentLtoV one or the .other4 of the trunk conductors depending on the class of the call, a relayv connected to each conductor of the'trunk at: theswitchboard. end and operated responsive toiringing cur-v rent transmitted over the associated conduc-- tor whena call is extended over the trunk. line, a signal yat the switchboard controlled by both relays, and a second signal at'ftheV switchboard controlled only byoneof the relays.

6. In a telephone system, an automatic switch for extending connections to lsubscribers lines and to trunk lines, a source o sig-- nalling current adaptedto be connected-'toI either side of any of said lines, means in said Switchfor determining the side ot the line to 4 which said current' source is to-be connected,- subscriber controlled means lfor -contrel-ling said first means in connections@.extended'to subscribers lines,` andm-eans' independent of lio lit

subscriber control-for controlling said iirs't means in connections vextended to trunk lines. -7. In a telephone system, an automatic switchequipped with a plurality of wipers `vforpextending calls, asource of signalling' current, a relay in the switch for determin-i ing the particular one of said wipers to which said current rsource is to be connected, subscriber controlled'means in the switch for operating said relay in certain calls, and means for operating said relay independent of said subscriber controlled means in certain other calls.

8. Inv a telephone system, an automatic switch .for extending calls to subscribers lines and to .trunk lines, an auxiliary switch associated with said first switch for selecting one of a plurality-of sources of ringing current to be applied to a called line, means for operating both of said switches to extend a call, a relay lin the first switch for determining the particular side of the called line to which the current source selected by the auxiliary switch is to be applied, means controlled by the auxiliary switch for operating said relay in calls to subscriberslines, andr means independentof said auxiliary switch forroperating said relay in calls to trunk lines.

9. Ina telephone system, a train of auto.- matic'switches for extending calls to subscribers lines and to trunk lines, an auxiliary ringing current switch associated with the lastV switch of thetrain, means for operating all: of said switches to extend a call, a relay in the last switch of the train for determining the particular side of the called line to which the ringing current selected by the auxiliary switch is to be applied, means for operating said relay responsive to the operation of the Y controlled means for operating said auxiliary switch in calls to subscribers lines, andantematic means I forA operating said auxiliary switch in calls to trunk lines.

11. In al telephone system, a two-motion automatic switch for extending calls to subscribers lines and to trunk lines, an auxiliary ringing current selectingvswitch associated with said first switch, means' controlled by a calling subscriber for directively operating thefirst switch in its primarT7 movement to extend a call, means controlled-by the calling subscriber for directively operating the firstvswltch 1n its secondary movement and for dircctively operating thc auxiliary switch provided the call is directed to another subscribers line, means for automatically-operating the first switch in its secondary movement provided the call is directed to a trunk line, and means for automatically operating the auxiliary switch provided the call is directed to a trunk line.

l2. Ina telephone system, a two-motion automatic switch for extending-calls to subscribers lines and to trunk lines of` two classes, an auxiliary ringing current selecting switch associated with said first switch, means controlled by a calling subscriber for directively operating the first switch in its primary movement in calls to any line, means controlled by a calling` subscriber for directively operating the first switch in its secondary movement and for directively operating the vauxiliary switch provided the call is directed to the subscribers line, means for automatically operating the first switch in its secondary movement provided the call is directed to a trunk line of either class, and meansfor lntomatically operating the auxiliary switch provided the call is directed to a trunk line of one class.

13. 'In a telephone system, an automatic switch for extending callsto subscribers lines and to trunk lines, an auxiliary switch associated with said first switch, a line relay, a primary stepping magnet and a secondary stepping magnet for the first switch, a stepping` magnet for the auxiliary switch, means for successively placing said magnets under control of said relay for extending a call to av subscribers line, and means for placing said primary magnet under control of said relay and for automatically operating said other magnets for extending a call to a trunk line.

14; In-a telephone system, an automatic switch adapted to connect with a called subscribers line responsive to the receipt of two series of digit impulses and to automaticallyv hunt for and connect with an idle trunk line responsive to the receipt of one series of' digit impulses, an auxiliary ringing current selecting switch associated with said first switch, means for rendering said auxiliary switch controllable by a third series of digit impulses when a. subscribers line is connected with, and means for operating said auxiliary switch independent of any further digit impulses when a trunk line is connected with.

15. In a telephone system, a two-motion first switch.

automatic switch and an associated auxiliary switch, means for directively operating the first switch in its primary movement, means normally effective for rendering the first switch subject to directive control in its secondary movement responsive to the completion of the primary movement, means operated responsive to the primary movement of the first switch to a particular position for disabling said second means and for causing the switch to be operated automatically in its secondary movement, means for rendering the auxiliary switch subject to directive control responsive to the completion of the directive secondary movement of the first switch, and means for automatically yoperating the auxiliary switch independent of directive control responsive to the completion of the automatic secondary movement of the 17. In a telephone system, an automatic switch and an associated ringing current selecting switch, means for loperating both switches to extend a connection to a called line, a release magnet for each switch for restoring the switchesto normal, a circuit for the release magnet of the auxiliary switch closed responsive to the termination of the connection, and means for transferring said circuit to the release magnet of the first switch responsive to the restoration of the auxiliary switch.

18. In a telephone system, a trunk selecting switch terminating a line, a trunk including two talking conductors and a holding conductor accessible to said switch, means responsive to a call on said line for operating said switch to connect the line with said trunk, means controlled over said holding conductor for maintaining the switch operated, and means controlled over said holding conductor for disconnecting said line from said switch to release the switch and said trunk.

19. In a telephone system, a trunk selecting switch terminating a line, a trunk including two talking conductors and a holding conductor accessible to said switch, means for operating the switch to seize said trunk responsive to an unstandard condition on said line, means in the switch for freeing both the switch and said trunk while said unstandard condition remains on the line, and a timing device associated with said trunk for operating said last means over the holding conductor of the trunk.

20. In a telephone system, lines terminating in trunk selecting switches, a plurality of trunk lines accessible to said switches, a timing device common to said trunk lines for releasing the trunk lines from connections extended thereto but not further extended for a predetermined interval, a relay for each trunk line, contacts controlled by the respective relays for connecting said device indi- NORMAN II. SAUNDERS. 

